ui: Use the desktop stylesheet for all screens

We don't have the other one anymore anyway...
ui: Show the album name in the album browser top bar
ui: Fix toolbar and buttons size in viewer
ui: Autohide the toolbar in viewer mode
ui: Add fullscreen mode in viewer (where supported)
albums: Add cache headers to picture thumbnails
ui: Factor URL hash navigation in app.js

This now also allows updating the hash without the router dispatcher
triggering, although we don't use that yet...
ui: Fix spurious album reloadings in Chrome

Chrome does not decode non-url-safe characters from the URL, which would
break album caching (and we'd reload the album everytime we switch
pictures in the browser).
ui: Preload neighbouring images in the viewer
ui: Don't reset browser album all the time
thumbnailer: Drop gographics' imagick and use a home made thumbnailer

imagick was good, but its extensive API coverage makes compiling the
binary on older platforms like CentOS a headache. Given the simplicity
of the calls we need, we can as well write the 30 lines of C code to
do what we need, and link that directly.